Addition of phytochemical-rich plant extracts mitigate the antimicrobial activity of essential oil/wine mixtures against Escherichia coli O157:H7 but not against Salmonella enterica

Authors: Friedman, Mendel; Levin, Carol; Henika, Philip

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2016
Publication Date: 3/4/2017
Citation: Friedman, M., Levin, C.E., Henika, P.R. 2016. Addition of phytochemical-rich plant extracts mitigate the antimicrobial activity of essential oil/wine mixtures against Escherichia coli O157:H7 but not against Salmonella enterica. Food Control. 73B:562-565. https://doi.org/10.1016/j.foodcont.2016.09.002.
DOI: https://doi.org/10.1016/j.foodcont.2016.09.002

Interpretive Summary: In the present and previous studies, we have reported our findings on the antibacterial activities of numerous wine formulations containing individual and combinations of food-compatible compounds: essential oils of oregano and thyme, and their bioactive compounds, which inactivate pathogens by disruptions of cell membranes; and plant extracts of apple and olive that inhibit growth of bacteria by antioxidative effects. Our hypothesis that the two different categories of antimicrobials might act synergistically was not borne out. Activities of the treatments against Salmonella enterica were greater than against Escherichia coli. Further studies should investigate the antimicrobial efficacy of the wine formulations against antibiotic-resistant bacteria as well as their sensory properties and compatibilities and applications in food, including as wine marinades, and as antimicrobial additives to liquid and solid food.

Technical Abstract: Red wine or fortified red wine formulations containing some various essential oils from oregano or thyme or their pure active components, and a mixture of plant extract powders from apple skin, green tea, and olive, were evaluated for inhibitory activity against the foodborne pathogens Escherichia coli O157:H7 and Salmonella enterica. Three independent assays were used to determine bactericidal activity of a dilution series: (a) BA50, defined as the percentage of the sample that resulted in a 50% decrease in the number of bacteria with an initial count of ~10e4 colony-forming-units (CFU)/mL; (b) the Dilution Factor Test, defined as the percentage of sample that resulted in a 50% decrease of bacteria with an initial concentration of ~10e9 CFU/mL; and (c) the Pellet Test, where the dilution series was prepared from an isolated bacterial pellet. Red wine alone and the same wine with additional ethyl alcohol (fortified) exhibited low activity. The activity of added oregano or thyme essential oils was reduced by addition of plant polyphenols when their concentration was 0.1% but not 0.025%. The assays can be used to measure the inhibition of both pathogens with low and very high initial CFU levels. The most active formulations merit further evaluation against antibiotic-resistant bacteria and for antimicrobial efficacy in liquid or solid food.